Vacuum IG units are known in the art. For example, see U.S. Pat. Nos. 5,664,395, 5,657,607, and 5,902,652, the disclosures of which are all hereby incorporated herein by reference.
FIGS. 1-2 illustrate a conventional vacuum IG unit (vacuum IG unit or VIG unit). Vacuum IG unit 1 includes two spaced apart glass substrates 2 and 3, which enclose an evacuated or low pressure space 6 therebetween. Glass sheets/substrates 2 and 3 are interconnected by peripheral or edge seal of fused solder glass 4 and an array of support pillars or spacers 5.
Pump out tube 8 is hermetically sealed by solder glass 9 to an aperture or hole 10 which passes from an interior surface of glass sheet 2 to the bottom of recess 11 in the exterior face of sheet 2. A vacuum is attached to pump out tube 8 so that the interior cavity between substrates 2 and 3 can be evacuated to create a low pressure area or space/gap 6. After evacuation, tube 8 is melted to seal the vacuum. Recess 11 retains sealed tube 8. Optionally, a chemical getter 12 may be included within gap 13.
A typical apparatus for pumping down and sealing of the VIG unit is disclosed in U.S. Pat. No. 7,244,480, the entire contents of which are incorporated herein by reference. In the FIG. 3 embodiment of the '480 patent, for example, while the whole VIG unit is in the atmosphere, the evacuation was accomplished through a pumping port tube using an upside-down cup connected to the vacuum system. Once the pump-down is completed, the pumping port is sealed by tipping off the tube using a device, which can be either a wire heater, or focused IR source, or a laser, or other heating devices.
To achieve good insulating characteristics, the vacuum cavity must be under vacuum, typically below about 1×10−1 torr. The vacuum is created by means of vacuum pump removal of gasses between the edge-sealed plates of glass through a vacuum port or pump-out port. Typically, the pump out port includes a small diameter glass tube inserted into a pre-drilled hole in one of the glass plates, which is affixed and sealed using a perimeter ceramic frit, solder glass, and/or by other means. Once the appropriate vacuum level is reached within the vacuum gap, the glass tube is melted on the exposed end with a heat source, thereby sealing the vacuum gap and maintaining the vacuum within the hermetically sealed glass plates. The time required to pump-down the VIG assembly to required absolute pressure is a function of the pump out tube hole diameter.
Conventionally, the hole has an outer diameter of less than about 5 mm and, typically, the hole outer diameter is only about 1-2 mm. The pump out tube diameter must be small in order to quickly melt the end and allow the glass wall to collapse upon itself in order to seal the tube. Ultimate vacuum may not be reached if the pump out tube diameter is too small. However, if the tube is too large, there often are difficulties associated with focusing a laser on the tube to cause the melting thereof.
Conventional sealing techniques, including laser-sealing techniques, disadvantageously trap radicals in the vacuum. For example, CO* radicals may be emitted from the carbonates in the glass into the vacuum. This causes a pressure increase within the gap between substrates, resulting in a degradation in the insulating characteristics of the assembled VIG unit (e.g., a substantially instantaneous reduction in R-value). Larger holes tend to trap more radicals. This degradation occurs in addition to the normal degradation caused when the VIG unit is exposed to UV radiation, as it is under normal conditions.
Thus, it will be appreciated that there is a need in the art for improved VIG units, and/or methods of making the same, that overcome one or more of these and/or other disadvantages. In addition, it also will be appreciated that there is a need in the art for pump-out ports having an increased diameter, improved vacuum and sealing techniques, and/or methods for the same.
In certain example embodiments of this invention, a method of making a vacuum insulating glass (VIG) window unit is provided. First and second spaced-apart glass substrates are provided, a gap being provided between the spaced-apart substrates. A pump-out port has a size (e.g., diameter) of at least about 30 mm. A cover for use in sealing the pump-out port is provided. Getter is in communication with the gap. The pump-out port is sealed using the cover, in making the vacuum insulating glass unit, via a sealing material provided proximate to the cover and/or proximate to the pump-out port.
In certain example embodiments, a vacuum insulating glass (VIG) unit is provided. First and second spaced-apart glass substrates are provided, and a gap is provided between the spaced-apart substrates. A pump-out port has a diameter of at least about 30 mm. A cover seals the pump-out port. Getter is in communication with the gap. The pump-out port is sealed using the cover, in making the vacuum insulating glass unit, via a sealing material provided proximate to the cover and/or proximate to the pump-out port.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.